Common to all horses are four basic gaits: walk, trot, canter, and gallop. Gaited horses throughout the world, however, possess the ability to perform certain alternate forms of movement relative to their breed. A team of Swedish researchers discovered that genetic makeup affects locomotion patterns in horses, allowing for gaitedness through two separate effects: extra gait in some breeds and fast trot in harness racing horses.

Studying Icelandic horses using genome-wide association analysis and whole genome resequencing, the team determined that a genetic mutation facilitates the lateral gaits ambling and pacing. “We managed to identify a novel gene, DMRT3, which regulates the pattern of locomotion,” explained Lisa Andersson, PhD, of the Swedish University of Agricultural Sciences, in Uppsala. “DMRT3 is specifically expressed in the spinal cord; we propose that the mutant variant somehow makes the spinal cord more flexible.”

The team concluded that homozygosity (possessing two identical forms of this gene, with one inherited from each parent) for the DMRT3 mutation is necessary for pacing. “Only Icelandic horses with two copies of the mutant gene variant can perform the two-beat lateral gait, flying pace,” explains Andersson.

The team noted this mutation is conducive to other gaits, such as ambling and pacing, in other gaited breeds besides the Icelandic. The mutation is also favorable for horses used in harness racing, as it allows them to trot at a higher speed before breaking into canter.

“It is now possible for any horse owner to test their horses for this gene-variant,” remarked Andersson. “This is particularly interesting if you have a cross breed or a breed where both gaited and nongaited individuals occur. Europe doesn’t have many different kinds of gaited breeds, but owners of Icelandic horses and Standardbred trotting horses are testing their horses.”

Interestingly, research from two different teams, one studying horses and one studying mice, reached similar conclusions. “We used the mouse to further characterize the function of the DMRT3 gene,” explains Andersson. “This helped us to establish the importance of this gene in gait regulation. Importantly, the fact that it regulates the pattern of movement in two such diverse species makes it a likely candidate for regulating movement in all vertebrate animals.

“This is the first time that a gene variant with an effect on horse locomotion is identified," she continued. "The gene variant has a significant influence on horse gait, and has had a dramatic effect on the diversification of the domestic horse. In addition, it adds to the basic knowledge of the regulation of movement in vertebrates—including humans.

“This breakthrough research has opened a whole new field of research," Andersson concluded. "How old is the mutation and when did it first occur? Are other mutations present in animals and/or humans with altered locomotion patterns? Exactly how does the gene influence cell function and ultimately locomotion? What is the frequency of the mutation in different horse breeds and what is the practical effect of the mutation in these breeds? There are many gaited breeds where we know the mutation is segregating but where we have yet to investigate its exact effect.”

The study, "Mutations in DMRT3 affect locomotion in horses and spinal function in mice," was published in Nature.

About the Author

Freelance journalist Natalie DeFee Mendik is a multiple American Horse Publications editorial and graphics awards winner specializing in equestrian media. She holds an MA in English from Colorado State University and an International Federation of Journalists' International press card, and is a member of the International Alliance of Equestrian Journalists. With over three decades of horse experience, Natalie’s main equine interests are dressage and vaulting. Having lived and ridden in England, Switzerland, and various parts of the United States, Natalie currently resides in Colorado with her husband and two girls.

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